1. Field of the Invention
The invention relates to a control device of a vehicular automatic transmission, and in particular to control executed when neutral control is cancelled.
2. Description of the Related Art
A vehicular automatic transmission is known which is operable under neutral control when certain neutral control conditions, for example, that a foot brake (brake pedal) is in the ON position and the vehicle speed is equal to zero, are satisfied while the shift lever is in one of running positions, such as D range. Under the neutral control, an engaging device provided in a power transmission path between an engine and driving wheels is caused to slip or is released when the neutral conditions are satisfied, so as to restrict power transmission through the power transmission path, thereby to reduce the idling load of the engine.
One example of control device for the above type of automatic transmission is described in Japanese Patent Application Publication No. 2000-304127 (JP-A-2000-304127). According to the technology disclosed in JP-A-2000-304127, when the accelerator pedal is operated (e.g., depressed) during cancellation of the neutral control, a target rate of change of a turbine speed is corrected to increase, so that an engaging device to be engaged upon cancellation of the neutral control is brought into an engaged state before racing of the engine takes place.
The technology for reducing shock by rapidly engaging the engaging device through correction of the oil pressure applied thereto during cancellation of the neutral control, as described in JP-A-2000-304127, is also described in, for example, Japanese Patent Application Publication No. 2000-304128 (JP-A-2000-304128) and Japanese Patent Application Publication No. 11-230327 (JP-A-11-230327). In any of the control methods described in the above-identified publications, the oil pressure applied to the engaging device is corrected uniformly or in the same manner irrespective of variations in the time at which the accelerator pedal is operated during cancellation of the neutral control; therefore, it is difficult to reduce shock with stability. Namely, during cancellation of the neutral control, an engaged state of the engaging device to be engaged and a shift stage in the process of shifting the automatic transmission naturally vary depending on a point in time at which the accelerator pedal is operated. However, according to the control methods as described in JP-A-2000-304127, JP-A-2000-304128 and JP-A-11-230327, the oil pressure is corrected uniformly or in the same manner without taking account of the above-mentioned variations; therefore shock may occur during cancellation of the neutral control, depending on the timing of operation of the accelerator pedal.